Lumbar curve response to selective thoracic fusion in adult idiopathic scoliosis.

Background: To date, no study has critically examined the radiographic characteristics of the lumbar curve after selective thoracic fusion for the adult idiopathic scoliosis patient population.

Objective: To evaluate the radiographic response of the lumbar curve to selective thoracic fusion in the adult scoliosis population with correlative clinical outcomes.

Methods: Retrospective case series. Methods: Thirty patients with idiopathic scoliosis surgically treated at a mean age of 40 years (range, 20-66) using a posterior translational technique. Methods: Radiographic review and functional outcome assessment. Methods: A retrospective, minimum 2-year follow-up, radiographic, and clinical review. All patients underwent selective thoracic posterior fusion with end-instrumented vertebra at T11 (1), T12 (7), L1 (14), and L2 (8).

Results: At a mean follow-up of 39 (range, 24-87) months, spontaneous lumbar curve Cobb improvement (36 degrees -18 degrees = 50% correction) was less than the bending radiograph (12 degrees , 68% correction). Lowest-instrumented vertebra (LIV) tilt angle improved from 24 to 9 degrees and LIV disc angle improved from 8 to 4 degrees (p < .001). Lumbar apical disc angle improved from 10 to 7 degrees (p < .001). Lumbar apical vertebral translation remained unchanged from pre-op (17 mm) to latest follow-up (17 mm) (p = .23). Lumbar curve rotation increased from 8 to 10 degrees (p = .11). One patient had coronal imbalance of greater than 3 cm and two patients had greater than 3 cm of negative sagittal imbalance. Mean subgroup scores of the Scoliosis Research Society-22 questionnaire improved (p < .01) for pain (3.0-3.8) and self-image (2.5-4.0) but remained the same for function and mental health. Only one patient required extension of fusion to include the lumbar curve 6 years postoperatively.

Conclusions: The lumbar curve response in adult, selective thoracic scoliosis surgery is characterized by 1) moderate correction but less than the bending film Cobb; 2) greater change in LIV tilt and disc angle than apical vertebra disc angle; 3) no change in lumbar apical translation or rotation; 4) more significant disc height preservation at the LIV compared with lumbar apex. Good clinical outcomes can be achieved with posterior translational instrumentation in adult scoliosis patients.